Adjustable crank means



Aug. 15, 1950 R. SNYDER ADJUSTABLE cmmx MEANS Filed Nov. 4, 1944 FIG. 1.

FIG. 3.

RICHARD L. SNYDER FIG. 2.

ATTORNEY Patented Aug. 15, 1950 UNITED STATES PATENT OFFICE (Grantedunder the act of March 3, 1883, as amended April 30, 1928; 3'70 0. G.757) 3 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to improvements in lapping machines.

Due to the enormous demand created by the war for crystals of thepiezoelectric type for frequency control purposes, mass productiongrinding methods have been developed. One important grinding or lappingmachine has evolved from the drill press and is capable ofsimultaneously lapping a large number of crystals on both sides. Everyeffort has been made to perfect these machines to save time andmaterials and to simplif the lapping operation.

Such a machine is provided with two, spaced, horizontally disposed,lapping plates, one above the other. Loosely positioned between saidplates is a crystal carrier which holds a plurality of crystals. Arotary motion is imparted to said crystal carrier by the spindle of thedrill press which operates through a small crank and thereby moves thecrystals between the lapping plates. 7 It has been found that suchmachines have the disadvantage of using the same crank for difierentsized crystals. In such operation, small crystals will not reach theinner and outer edges of the lapping surfaces and large crystals will gobeyond said edges. An adjustable eccentric, small in size, simple tooperate, requiring a minimum of machining and requiring a minimum ofmaterial (in view of the shortage of materials, tools and labor due tothe war effort) is desired.

It is, therefore, an object of the present invention to provide anadjustable eccentric which is small in size and simple in operation.

It is another object to provide an adjustable eccentric which requires aminimum of material and machine work to manufacture.

It is a further object to provide an adjustable eccentric for a crystallapping machine which will allow machines in present use to beefficiently used for lapping crystals of different sizes so that theymay be adjusted to utilize the full lapping surfaces irrespective ofcrystal size.

It is a further object to provide an adjustable eccentric which isreadily variable from zero to maximum eccentricity.

It is another object of this inventionto provide an adjustable crank armwherein the depending pin at the outer end of the said arm may bereadily replaced when worn, without requiring unnecessary labor andmachining.

It is still another object to provide an adjustable crank arm which. maybe adjusted without the likelihood of breakage of crystals or othervparts. i v V In crystal grinding machines generally, under usualquantity production arrangements, the operator has access to themachineconvenientlyon1y from one direction which may be termed thefront. crank will stop in various positions, and a large number of thesepossible positions are not convenient for access to the fastenings bywhich the crank elements are secured in their adjusted radius positions.The same is true of adjustment of holders and cranks for varyingthicknesses of crystals. This is particularly true in the drill pressmachines, where the usual standard or post (springing from the drillpress base and carrying the spindle and its drive)- will prevent thepresentation of the hand or a tool from the rear or eiiectively from awide range of angles toward the sides Where a bank of such machines isset up in close relation side by side, also, there is considerable riskof injury to the operator by the next machine if an attempt is made topresent a tool from either side, as well as involving danger ofdisturbance of adjustments on the neighboring machine by impact of itsparts against the arm or garments of the operator.

, On this account, it is an object of the invention to evolve a simple.and low cost device having the capabilities of adjustment required, ofradius and height of an eccentric which will at the same time affordaccess to fastenings on the adjustment from opposite sides, so that ifone such fastening is exposed toward the rear in such machines therewill also be afforded access from the front to an equivalent fastening;andat the same time to keep these fastenings in the smallest,

tricity. As the auxiliaryv crank maybe locked at an position,intermediate thesetwo extremes,

any amount of eccentricity .therebetween may be readily obtained. I

The n vel ieatures which it is believed are In the stopping of themachine, the

posed .circulan bores 69,, I l

characteristic of this invention are set forth with particularity in theappended claims, but the invention itself will best be understood byreference to the embodiment set forth in the following description takenin connection with the accompanying drawings, in which:

Figure. 1 is a -perspec.tive view: of the lower 'portion of a crystallapping machine embodying the present invention, wherein the adjustableeccentric is shown in its fully extended position, andpart of the upperlapping plate is cutaway for clarity;

Figure 2 is an enlarged perspectiveview of the adjustable eccentric ofFigure 1,, wherein it is shown adjusted for relativelysm'a'll"eccentricity and Figure 3 is a vertical radial crosssectionalview of thesaid adjustable eccentric; wherein it is shown adjusted for maximumeccentricity.

The lapping machine; shown in the drawings, stands-uponabasal I,having-a fiat, horizontally disposed, top surface ['33 Resting uponsaid' sur face [3 is. a metal, disc-like, planiform lower lappingplate'I5, the'top, flat, horizontalsurface l1 of 'which forms the lower"lapping surface of" the machine: Positioned about the lower lappingplate I5 arefouraligning brackets l9, each of which issecure'dv to thebase I I by' means of a machine screw 2'1.

Spaced above "the? lower lapping plate l5i's a metal annular upperlappingplat'e 23 of the same diameter, thelower,:flat,horizonta'lsurface' 25 of which f'o'rrns"v the; upper lapping' surfaceof the machine." The central portionof said upper lapping plate.23iscut' out'tb ifoi'ma circular aperture 21 concentric with" theplates outer periphery. Said: upper lappingplate 23 is also providedwith two liftinghandles 29: Theoute'r periphery of said upper lappingplate 23' 'is pierced by four horizontally disposedfholes', into each ofwhich is inserteda; spacerbar 51; The outerreduced ends of s'aid',spacer-bars 5F extend" respectively into vertical stS149, in thebrackets 1'9, and they (and' consequentlyalso the plate'23i are'free tomove vertically in" said" slots,

Interpos'ed between, the" two lapping, plates 23' are a plurality of"crystals 3| to be lapped. Said crystals 3| are .retainedin'spacedrelationship relative to each otherlbya. carrier 33 which is.a dis'cofinsul'ating, material} such as Bakelite,

.of. smaller diameter than the lapping plates 55, 23 (but of;substantiallygreaterdiameter than the aperture. 21),, an'd'piercedbyasmallcircular axial hole 36 and a plurality of holes 35 shaped toloosely ,receive' the crystals" 3l. The carrier; 33

.is not as thick as the crystals..3l 'which are to be lapped." Themachinenia'y'be provided with several carriers 33 ofdifierentthicknesses and having difierent sized'h'ole's" 35' s'o'that'a suitable.carrier maybe. used. in. lapping, crystalsof a particular thickness andsize.

Axially positionedab'ove' the lapping plates I5,

Secured to the centric 39' fitted'with a" depending-wrist pin 4'! whichi'sof'a size tomakea' rotatablefit inthe center hole -36 [ofith'ecarrier .33.

The. adjustable eccentric". 39 comprises the upper-main...andlradialcrank 38 and the lower auxiliary. and? variable-radius crank 40L Themain'crank' 38"is pierced'bytwo vertically dis- The'iauxiliary crank 40is similarly piercedby two vertically" di p s d.

circular bores l3, l5. Formed in the ends of the respective cranks atright angles to each of said bores 69, ll, l3, l5, and communicatingrespectively therewith, are horizontally disposed, threaded, set screwholes TI, 19, 8|, 83, each of which holes receives a set screw 85. Thelower end of the. spindle 31 fits into the-bore 69. A single straight,circular knuckle pin 8'! fits into the apertures H, 73. A secondstraight, circular pin, which is the wrist pin 4! before mentioned, fitsinto the aperture 15 and extends downwardly beyond said aperture. Saidspindle 31, and said pins 8T, M are held and locked in place by the fourset screws aforesaid. It may be noted from Fig. 3 that pins 81 and H areof approximately the same diameter, so that assembly is corre-Spondingly simplified.

Inoperation of the lapping machine, shown in the drawings, the twolapping plates I5, 23 are disposed in register, the carrier 33 and thecrystals' 31 being so positioned between the lapping plates i5, 23 thatthe crystals 3! will move over the full width ofthe lapping surface 25,but will not go beyond the edges thereof. The set screw 85 in the setscrew hole 19 is then loosened and, while the auxiliary crank 48 isbeing supported in place manually, the spindle 31 is moved downwardlyuntil the depending pin 4| is lowered into the center hole 36 of thecarrier 33, through the central aperture 2'5. The said set screw 85 inthe set screw hole 39 is then tightened. Rotation of the spindle 31 bymeans of the motor (not shown) will then cause'the crystals 3! to moveabout horizontally between the upper and lower lapping surfaces ll, 25,a suitable grinding compound being applied.

It is'readily seen that the parts of the adjustable eccentric justdescribed' require a minimum of machining, that the eccentricity isreadily adjustable and that any parts which may wear may be easily andinexpensivel replaced, such wear usually occurring mainly in thedepending pin 4 l.

Although the embodiment herein described, to illustrate the presentinvention, is shown in connection with a crystal lapping machine. Itwill be understood that it is within the spirit of the invention toapply it to other lapping or grinding machines and to other uses.

What is claimed is:

1. In a crystal grinding machine of the character described, wherein avertical spindle is operable over a bottom planiform grinding platehaving an annular planiform grinding plate vertically free thereover,and wherein a' circular crystal carrier is free between the plateshaving avariable radius eccentric connection with said spindle;. animproved variable throw crank to connect the spindle and carriercomprising an upper crank arm constructed to be fixed to the spindle, avertical bore therethrough adjacent its outer end, a knuckle pinslidable'therethrough, pinlocking means on the arm having an operatingpart exposed outwardly on the radius of the arm, a lower crank armhaving a vertical bore therethrough adjacenteach end, either ofthelastnamed. bores being capable of receiving slidably therethrough saidpin, a wrist pin slidable alternatively in said holes of the lower crankarm to project therebelowand engage the carrier, and respective.pin-locking means at the. ends of the lower crank arm having, respectiveoperating parts exposed longitudinallyon the ends of the arm andconstructed for operation by a tool-while positioned approximatelyalong, the longitudinal axis of the respective arm.

2. The structure of claim 1 wherein each said pin-locking meanscomprises an operating member set in the extremity of the respective armaccessible by a tool presented approximately in alignment with thelongitudinal axis of the arm.

3. The structure of claim 1 wherein the said upper crank arm isvertically bored to receive the spindle slidably therethrough, and. aspindlebinding member thereon exposed radially opposite the outer end ofthe arm.

RICHARD L. SNYDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

6 UNITED STATES PATENTS Number Number 10 348,286

, Name Date Wanzer Nov. 9, 1869 Crutchlow May 16, 1899 Siddle Sept. 8,1925 Christiansen Sept. 10, 1940 FOREIGN PATENTS Country Date Italy May15, 1937

